Single Channel Per Carrier (SCPC) point to point satellite communications require rigorous control of certain parameters to establish and maintain the satellite link. Some of those parameters are the transmit and receive radio frequency (RF) of the carrier, the intermediate frequency (IF), symbol or data rate, modulation type, error correction type and rate, and power transmit level. Some of those parameters, like the transmit and receive RF, are set and remain constant over long periods of time, while others, like transmit power and symbol rate, are changed on a more frequent basis to compensate for changed environmental conditions or customer needs. Network management control centers, which monitor multiple SCPC satellite links, are established to accommodate those more dynamic changes that maintain the end-to-end satellite communication service at optimal efficiency in response to customer needs.
A network management control center frequently consists of a computer that is physically connected to one or many local satellite control modems with some form of electronic connection. The electronic connection might be a simple twisted wire pair, some form of local area network, or a dial-up land line connection using the public switched telephone network (PSTN). When the network management control center is connected to the local satellite control modem with a dial-up land line connection via the PSTN, two conventional telephone type modems, one at the network management control center and one at the local satellite control modem replace the twisted wire pair or local area network connection. This arrangement also requires a PSTN connection between the network management control center and the local satellite control modem. Using any of the connections described, the local satellite control modems can generally be programmed from the network management control center with the parameters described above (IF, symbol rate, modulation type, power, etc.).
To support management of the SCPC satellite link, where one end of the link is connected to a network management control center through a local satellite control modem, a small portion of the channel bandwidth is often allocated to an "overhead" channel. This overhead channel is used by both satellite control modems to pass operational status and statistics messages, and also allows the network management control center to monitor and control the distant satellite control modem.
Typically, a network management control center will establish threshold levels or trend profiles for certain parameters which will alert an operator in the network management control center that action or intervention may be required. The operator can also typically select or monitor any of the managed SCPC satellite links for anomalies or trends that do not trigger an alert. If an anomaly or trend is identified that requires corrective action, that same overhead channel which exchanges statistics between the satellite control modems can also be used to implement changes in some of the parameters that were described above.
An example using the overhead channel to implement changes in a parameter might be where the network management control center determines that the transmit power level at the distant satellite control modem needs to be increased because the BER has increased to an unacceptable level. In that case, an operator at the network management control center could pass a new power level parameter to the distant satellite control modem through the overhead channel. That new power level parameter would be stored in a future data parameter area at the distant satellite control modem awaiting activation. After verification that the new power level parameter stored in the future data parameter area was properly received, the network management control center could use the overhead channel to command that new power level parameter from the future into the active data parameter area, where it would increase the transmit power level at the distant satellite control modem. If that step successfully resolved the BER problem, the operator at the network management control center could then command the distant satellite control modem, through the overhead channel, to write that new power level parameter in the distant satellite control modem, from the active data parameter area to NVRAM where it would remain indefinitely. That new power level parameter, now stored in NVRAM at the distant satellite control modem would be used for any subsequent reset or power-up.
The methods described above allow a single network management control center to monitor and control multiple SCPC satellite links without routine visits to the distant satellite control modems. This centralized network management has the advantage of keeping manpower costs low, while providing an ability to rapidly change parameters in response to environmental factors or user requirements. However, there are certain limitations in the methods described. Physical connection of the network management control center and local satellite control modem with either twisted wire pairs, or a form of local area network becomes more difficult and costs increase dramatically as the distance between the network management control center and the local satellite control modem increases beyond a few miles. The alternative, use of two telephone type modems and the PSTN does extend the range for network management, but requires additional hardware with associated expense, as well as access to the PSTN, with associated expense.
Existing methods and systems do not provide responsive network management services to SCPC remote satellite control modems that lack physical connections (e.g. twisted wire pair, local area network, or dial-up land line connection). Those remote satellite control modems require periodic visits during which the overhead channel described above is monitored and parameter changes are implemented. Those individual site visits entail travel time and are significantly less responsive than a centralized network management control center in implementing parameter changes to accommodate environmental effects or satisfy dynamic customer needs.